heap.c revision 9c3531d72aeaad6c5f01efe6a1c82023e1379e4d
/*
* Copyright (C) 1997-2000 Internet Software Consortium.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
* ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
* CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
* DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
* PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
* ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
* SOFTWARE.
*/
/* $Id: heap.c,v 1.24 2000/06/22 21:56:56 tale Exp $ */
/*
* Heap implementation of priority queues adapted from the following:
*
* _Introduction to Algorithms_, Cormen, Leiserson, and Rivest,
* MIT Press / McGraw Hill, 1990, ISBN 0-262-03141-8, chapter 7.
*
* _Algorithms_, Second Edition, Sedgewick, Addison-Wesley, 1988,
* ISBN 0-201-06673-4, chapter 11.
*/
#include <config.h>
#include <isc/heap.h>
#include <isc/mem.h>
#include <isc/string.h> /* Required for memcpy. */
#include <isc/util.h>
/*
* Note: to make heap_parent and heap_left easy to compute, the first
* element of the heap array is not used; i.e. heap subscripts are 1-based,
* not 0-based.
*/
#define heap_parent(i) ((i) >> 1)
#define heap_left(i) ((i) << 1)
#define SIZE_INCREMENT 1024
#define HEAP_MAGIC 0x48454150U /* HEAP. */
#define VALID_HEAP(h) ((h) != NULL && \
(h)->magic == HEAP_MAGIC)
/*
* When the heap is in a consistent state, the following invariant
* holds true: for every element i > 1, heap_parent(i) has a priority
* higher than or equal to that of i.
*/
#define HEAPCONDITION(i) ((i) == 1 || \
! heap->compare(heap->array[(i)], \
heap->array[heap_parent(i)]))
struct isc_heap {
unsigned int magic;
isc_mem_t * mctx;
unsigned int size;
unsigned int size_increment;
unsigned int last;
void **array;
isc_heapcompare_t compare;
isc_heapindex_t index;
};
isc_result_t
isc_heap_create(isc_mem_t *mctx, isc_heapcompare_t compare,
isc_heapindex_t index, unsigned int size_increment,
isc_heap_t **heapp)
{
isc_heap_t *heap;
REQUIRE(heapp != NULL && *heapp == NULL);
REQUIRE(compare != NULL);
heap = isc_mem_get(mctx, sizeof *heap);
if (heap == NULL)
return (ISC_R_NOMEMORY);
heap->magic = HEAP_MAGIC;
heap->mctx = mctx;
heap->size = 0;
if (size_increment == 0)
heap->size_increment = SIZE_INCREMENT;
else
heap->size_increment = size_increment;
heap->last = 0;
heap->array = NULL;
heap->compare = compare;
heap->index = index;
*heapp = heap;
return (ISC_R_SUCCESS);
}
void
isc_heap_destroy(isc_heap_t **heapp) {
isc_heap_t *heap;
REQUIRE(heapp != NULL);
heap = *heapp;
REQUIRE(VALID_HEAP(heap));
if (heap->array != NULL)
isc_mem_put(heap->mctx, heap->array,
heap->size * sizeof (void *));
heap->magic = 0;
isc_mem_put(heap->mctx, heap, sizeof *heap);
*heapp = NULL;
}
static isc_boolean_t
resize(isc_heap_t *heap) {
void **new_array;
size_t new_size;
REQUIRE(VALID_HEAP(heap));
new_size = heap->size + heap->size_increment;
new_array = isc_mem_get(heap->mctx, new_size * sizeof (void *));
if (new_array == NULL)
return (ISC_FALSE);
if (heap->array != NULL) {
memcpy(new_array, heap->array, heap->size * sizeof (void *));
isc_mem_put(heap->mctx, heap->array,
heap->size * sizeof (void *));
}
heap->size = new_size;
heap->array = new_array;
return (ISC_TRUE);
}
static void
float_up(isc_heap_t *heap, unsigned int i, void *elt) {
unsigned int p;
for (p = heap_parent(i);
i > 1 && heap->compare(elt, heap->array[p]);
i = p, p = heap_parent(i)) {
heap->array[i] = heap->array[p];
if (heap->index != NULL)
(heap->index)(heap->array[i], i);
}
heap->array[i] = elt;
if (heap->index != NULL)
(heap->index)(heap->array[i], i);
INSIST(HEAPCONDITION(i));
}
static void
sink_down(isc_heap_t *heap, unsigned int i, void *elt) {
unsigned int j, size, half_size;
size = heap->last;
half_size = size / 2;
while (i <= half_size) {
/* Find the smallest of the (at most) two children. */
j = heap_left(i);
if (j < size && heap->compare(heap->array[j+1],
heap->array[j]))
j++;
if (heap->compare(elt, heap->array[j]))
break;
heap->array[i] = heap->array[j];
if (heap->index != NULL)
(heap->index)(heap->array[i], i);
i = j;
}
heap->array[i] = elt;
if (heap->index != NULL)
(heap->index)(heap->array[i], i);
INSIST(HEAPCONDITION(i));
}
isc_result_t
isc_heap_insert(isc_heap_t *heap, void *elt) {
unsigned int i;
REQUIRE(VALID_HEAP(heap));
i = ++heap->last;
if (heap->last >= heap->size && !resize(heap))
return (ISC_R_NOMEMORY);
float_up(heap, i, elt);
return (ISC_R_SUCCESS);
}
void
isc_heap_delete(isc_heap_t *heap, unsigned int i) {
void *elt;
isc_boolean_t less;
REQUIRE(VALID_HEAP(heap));
REQUIRE(i >= 1 && i <= heap->last);
if (i == heap->last) {
heap->last--;
} else {
elt = heap->array[heap->last--];
less = heap->compare(elt, heap->array[i]);
heap->array[i] = elt;
if (less)
float_up(heap, i, heap->array[i]);
else
sink_down(heap, i, heap->array[i]);
}
}
void
isc_heap_increased(isc_heap_t *heap, unsigned int i) {
REQUIRE(VALID_HEAP(heap));
REQUIRE(i >= 1 && i <= heap->last);
float_up(heap, i, heap->array[i]);
}
void
isc_heap_decreased(isc_heap_t *heap, unsigned int i) {
REQUIRE(VALID_HEAP(heap));
REQUIRE(i >= 1 && i <= heap->last);
sink_down(heap, i, heap->array[i]);
}
void *
isc_heap_element(isc_heap_t *heap, unsigned int i) {
REQUIRE(VALID_HEAP(heap));
REQUIRE(i >= 1 && i <= heap->last);
return (heap->array[i]);
}
void
isc_heap_foreach(isc_heap_t *heap, isc_heapaction_t action, void *uap) {
unsigned int i;
REQUIRE(VALID_HEAP(heap));
REQUIRE(action != NULL);
for (i = 1; i <= heap->last; i++)
(action)(heap->array[i], uap);
}